Every serious war novel has two serious conflicts embedded in it. One involves combat, of course. The other involves words. Civilians are practically trained not to ask veterans "What was it like there?" because the answer is impossible to articulate. That impossibility complicates every story about war: How to explain the inexplicable? Kevin Powers' stark debut novel about the Iraq war, "The Yellow Birds," is informed and energized by this tension. It thrives on a narrator who's grimly aware that "what is said is never quite what was thought, and what is heard is never quite what was said."

That narrator is John Bartle, an Army private stationed in Iraq who helplessly watches a fellow soldier, Daniel Murphy, slowly go mad. There is no single incident that sends "Murph," still a teenager, off the rails. War itself is too plotless for that, and it has a way of turning traditional definitions of sanity and madness inside out. (The novel's title itself captures this upside-down-ness: An epigraph reveals its pastoral image to be a line in a violent marching cadence.) "How can you measure deviation if you don't know the mean?" John asks himself. "There was no center in the world."

Powers, himself an Iraq vet, shifts the story back and forth in time from Iraq to stateside to deliberately fog the truth about Murph's fate and John's complicity in it. Powers earns the right to shuffle the deck through the clarity of his sentences: His flat, affectless prose is a barrier against piety and sentiment, but when John's emotions run free the lines gain a run-on rhythm that's practically biblical in authority. "Why not just find a spot and curl up and die and let's make it as painless as possible because you are a coward and, really, cowardice got you into this mess because you wanted to be a man," goes part of a sentence that runs two full pages, a spume of fury after years of keeping emotions in check.

"The Yellow Birds" has the outward simplicity of a fable, and it captures the collision of camaraderie and grotesque violence that's all but required in every war story. But beneath its veneer of clean prose is a complex reckoning with how much words matter. John has told a handful of lies in Iraq, and the novel's strength is in his messy response to them; by turns he ignores his words, rationalizes them and dares himself to see them clearly. Powers' novel is sharp fiction about the act of fictionalization. No honest war story, Powers means to say, has time to waste on patriotism or machismo. The genuine drama is in the stories its players tell themselves to survive.